Combustion system for gas turbines with heat exchangers



Dec. 23, 1952 A. T. BbwDEN 2,

COMBUSTION SYSTEM FOR GAS TURBINES WITH HEAT EXCHANGBRS Filed Jan. 6, 1948 2 SHEETS-SHEET l A. 1'. BOWDEN COMBUSTION SYSTEM FOR GAS TURBINES WITH HEAT EXCHANGERS Dec. 23, 1952 2 SHEETSSHEET 2 Filed Jan. 6, 1948 Patented Dec. 23, 1952 narro- STAT-ES ENT ric-E COItEBUSTION SYSTEM FOR GAS TURBINES WITH HEAT EXCHANGERS 2 Claims.

This invention relates to combustion systems "for 'gas, turbines with heat exchangers of the kind incorporating a'combustion chamber having one or more fuel atomisers for spraying fuel whichis burnt'ina'stre'am'of air which 'has'been compressed'to the higher pressure of the cycle and wherein down-stream of the primary region further air is added but not in sufficiently large quantities to quench the flame before combustion is complete. Whencombustion is complete, the remainder of the excess air required for maintaining the design conditions of the turbine is added. All suppliesof air are at the higher pressure of the cycle. Usuallymeans are employed to stabilise the position of the flame by air currents created perhaps by the primary supply of air which is a little more than enough to complete burning. In such systems in consequence of the comparative nearness of the burner to the primary combustion region unburnt products and soot are liable to deposit on the burner face and ultimately form a more or less hard carbon layer which, by obtruding on the lip of the spray orifice, may ultimately spoil the spray in quality and distribution with consequent bad effect on the combustion processes and the endurance of the chamber components.

This effect is usually overcome in simple cycle plants by ducting an extra supply of fresh air over the face of the burner thus keeping it cool and combating any tendency for soot or other combustible to deposit on the burner.

In plants using heat exchangers that take heat from the gas exhausted from the turbine and put it into the flow of higher pressure air from the compressor the combustion chamber is supplied with air at a temperature higher than the normal temperature of the air delivered by the compressor. Such temperatures may approach the turbine exhaust temperature and may be above the cracking temperature of the oil fuels used.

A supply of this high temperature air if ducted round the burner in the usual way may not give the desired protection from carbon deposition and certainly will not aid the cooling of the burner nozzle to reasonable temperatures.

The object of the present invention is to overcome this difficulty.

The invention consists in a combustion chamber for gas turbines incorporating features set forth in the claims appended hereto.

Referring to the accompanying diagrammatic drawings:

Figure 1 shows diagrammatically a combustion system embodying the present invention,

Figure 2 is a vertical sectional view of a combustion chamber in connection with which by way of example the present invention may be applied.

Figure 3 is asimilarvie'w of "a burner, and

Figure 4 'isan end view of the burner, Figure 3.

Reference to Figure 1 will show how the invention is carried into effect according to one form by way of example.

referring to Figurel, in common practice the whole of the 'air'delivered from a compressor C at at point 'A is led through a heat exchanger H where it is heated by hot gas exjhausted from a turbine T and 'is thereafter led to a combustion chamber, CC. In accordance with this invention, in addition to air for primary combustion being constituted by air from the compressorC "after 'it hastraversed the heat exchanger H, a proportion of the total air delivered rrcmthe compressor is tapped at point P and led either "directly by the path PQRSTM or indirectly through an air conditioner AC by the path PQTM to cool the burner before it finally enters the primary zone of the combustion chamber CC.

As indicated in Fig. 1, the air conditioner A is a second and independent heat exchanger having a circuit QTconnectedinto the conduit and having surfaces in heat exchanging relation to the airfpja'sslng therethrough. .By circulating suitable. fluid through the cooperating 4 circuit the air, may be cooled or its temperature may be otherwise regulated v p I V The function of the air conditioner AC is by means of a heating or cooling medium directly or indirectly to supply heat to or extract heat from the aforesaid air. By suchmeans if desired, the air may be made available at even lower temperatures than the exit temperature from the compressor. The pressure drop which occurs over even the most efiicient heat exchanger is available for forcing this supply into the combustion chamber and any prior cooling arrangements which may be desirable.

Alternatively, by supplying heat to the air, the air conditioner may be used to improve the starting conditions for a gas-turbine plant using a heat exchanger. In such plants the usually considerable mass of the heat transfer elements of the heat exchanger take a substantial time to reach the stable temperatures natural to the conditions under which the plant is operating.

For a plant starting from cold condition, therefore, the heat exchanger will act as a cooler to the air coming from the compressor which has been slightly warmed by the compression. By utilising the same artifice of bleeding the special supply of air from before the heat exchanger, the region of the burner spray may be supplied with warm air which is in general more likely to produce ideal combustion conditions than cold air.

In Figure 2 is shown a combustion chamber of a type suitable for industrial type gas turbines and in connection with which the invention may be applied by way of example. Air, after compression and passage through the heat exchanger, is brought to the inlet A. By means of the snout B part of the total air entering through A is led through the primary air supply ports P, through the hollow sleeve S and thence through a swirler C to the primary combustion zone of the combustion chamber. Secondary air also brought in through the snout B, passes through the annular space D between the inner shell E and cone F. The tertiary or diluent air passes between the outer shell and inner shell E. The burner M passes through the hollow sleeve S and the swirler C.

Figure 3 shows in greater detail the location of the burner in the combustion chamber and parts common to Figure 2 are commonly indicated in Figure 3. In Figure 3, oil under pressure is supplied to the burner M by means of a pipe V. The particular burner shown is of the spill type wherein the quantity of oil fed to the burner is governed by the amount spilled or released through the return line W. The burner together with the inlet and outlet pipes leading thereto is contained within a cage consisting of an inner tube L and an outer tube R., The outer tube R is located in the swirler C and air either direct from the compressor or such air after having traversed the air conditioner AC is fed to the cage through the air inlets TT passes between the inner tube L and the burner pipes VW. and thence through the space J between the burner M and outer tube R to be directed as indicated by the arrows over the face of the burner.

By this means the burner is kept cool while in operation by using the air bled as aforementioned after delivery from the compressor but prior to entry to the heat exchanger, additionally cooled if required directly or indirectly by a cooling medium in the air conditioner AC.

Alternatively, the said air may be heated directly or indirectly in said air conditioner to assist the combustion process when starting the gas turbine.

I claim:

1. In a combustion system for gas turbines incorporating a combustion chamber having a fuel atomiser for spraying fuel which is burnt in a stream of combustion air which has been brought by a compressor to the higher stage pressure of the cycle and heated in a heat exchanger by the exhaust gas, a passageway in said fuel atomiser for cooling air, a conduit from said compressor to said passageway, said conduit by-passing said heat exchanger, and a heat exchanger comprising a circuit connected into the conduit and having heat exchanging surfaces in heat exchanging relation to the air passing therethrough.

2. In a combustion system for gas turbines having a compressor and turbine and heat exchangers including a heat exchanger for heating air delivered from the compressor before delivery to a combustion chamber by means of hot gas exhausted from the turbine, and in combination, a connection from the compressor bypassing the heat exchanger which heats the air delivered from the compressor to the combustion chamber, and serving to supply air from the compressor for ducting over a burner in the combustion chamber, the combustion chamber including a shell defining a primary combustion zone and receiving heated air from the compressor byway of the heat exchanger, a spray-type burner within the primary combustion zone and having a fuel supply pipe, a sleeve connectionto the by-pass connection and surrounding the fuel supply pipe for ducting bypassed air from the compressor around the burner, and a further sleeve surrounding the first said sleeve and having ports for receiving heated air from the heat exchanger and delivering the same tothe primary combustion zone with in the shell at the burner.

ANDREW THOMSON BOWDEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,245,954 Anxionnaz June *17, 1941 2,390,959 Pfenninger Dec. 11,1945 2,396,068 Youngash Mar. 5, 1946 2,411,181 Altorfer Nov. 19, 1946 FOREIGN PATENTS Number Country I Date 210,658 Switzerland Oct. 1, 1940 212,269 Switzerland Feb. '17, 1941 377,849 Great Britain Aug. 4, 1932 

